JP5807778B2 - Steering device for cargo handling vehicle - Google Patents

Description

The present invention relates to a steering device for a cargo handling vehicle used in a cargo handling vehicle such as a forklift.

Forklifts often turn around corners close to a right angle. When turning around a corner close to a right angle, the rear wheel of the forklift is a steered wheel. Turn the front (fork) lightly in the direction of turning at a small steering angle, and then turn the rear with a sharp steering. The steering operation peculiar to a forklift that swings outside is performed.
On the other hand, the forklift employs a so-called steer-by-wire type power steering device in which the mechanical connection between the steering member provided in the cab and the rear wheel as the steered wheel is cut off. Therefore, there is essentially no reaction force returned from the rear wheel to the steering member. Therefore, conventionally, a simulated reaction force was created on the steering side and returned to the driver.

  Further, the stroke ratio, which is the ratio between the steering angle of the steering wheel and the turning angle of the steered wheels, has been conventionally set to a proportional relationship (Patent Document 1).

JP 2010-264833 A

Forklifts have a wide range of steering angles and a high frequency of steering for their applications. Therefore, the driver's steering wheel operation amount is large and the burden is large.
The simulated reaction force created on the steering side increases linearly with the steering angle up to a certain steering angle as shown in the graph of “conventional characteristics” in FIG. There are characteristics. For this reason, in the initial stage of turning, the reaction force is too small and the steering force overcomes the reaction force, and the steering angle often becomes larger than the steering angle intended by the driver. In the latter half of the turn, the vehicle must be steered suddenly. However, a large reaction force required a force to steer suddenly, placing a burden on the driver. For this reason, there was a problem that the work efficiency was lowered.

The present invention, by appropriately setting the reaction force characteristics to the steering angle, and an object thereof is to provide a steering equipment for cargo handling vehicle which can reduce the steering load of the driver.

Steering device for a cargo handling vehicle of the present invention, there is provided a steering device for a cargo handling vehicle employing a steer-by-wire type which mechanical connection is interrupted between the steering member and the steered wheel drive mechanism, the rolling to steer the steered wheels a steering wheel driving mechanism, wherein the steering angle detection unit that detects a steering angle of the steering member, a reaction force actuator that imparts a steering reaction force to the steering member, a steering actuator for driving the steered wheel drive mechanism, the rolling A steering actuator controller that controls the rudder actuator and whether the steering angle is in the first rudder angle region that is equal to or smaller than the first switching angle or in the second rudder angle region that exceeds the first switching angle A steering area determination unit that increases the steering reaction force to the maximum value as the steering angle increases when the steering angle is in the first rudder angle area, and steers when the steering angle enters the second rudder angle area. The steering reaction force decreases from the maximum value as the angle increases. It is intended and a reaction force actuator control unit that controls the reaction force actuator such that.

According to this configuration, when turning a corner, if the region where the steering angle exists when the front part is lightly turned in the turning direction with a small steering angle is set as the first steering angle region, the steering angle is Since the steering reaction force rises to the maximum value as the value increases, the driver feels a large reaction force while turning the steering wheel. Therefore, there is little risk of turning the steering wheel too much beyond the driver's intention. By setting the region where the steering angle is present in shake rear with quick steering the corner outside the second steering angle range, in this region, the steering reaction force with an increase in the steering angle is decreased by a maximum value or al Therefore, the driver feels that the reaction force decreases as the steering wheel is turned. Therefore, since the driver can steer the vehicle with a small force, the steering burden on the driver can be reduced.

A second switching angle larger than the first switching angle is set, and the steering actuator control unit determines that the ratio of the steering angle to the steering angle is the steering angle from the first switching angle to the second switching angle. It is preferable to control the steered actuator so as to take a first inclination up to the switching angle and to take a second inclination smaller than the first inclination when the steering angle is equal to or larger than the second switching angle. In the case of the prior art, the first inclination and the second inclination are the same value. However, in the present invention, since the first inclination> the second inclination, the first half of the second steering angle region (the first inclination) (From 1 switching angle to 2nd switching angle), the stroke ratio is large and the steering becomes easy. In the second half of the second rudder angle region (greater than or equal to the second switching angle), the stroke ratio becomes small and the steering becomes gentle. Therefore, as described above, when in the second steering angle range, by setting cooperation of the steering reaction force with an increase in the steering angle is gradually decreased by a maximum value or al, driver less Since it is possible to steer quickly with force, the steering burden on the driver can be reduced.

It is a typical side view which shows schematic structure of a forklift. It is a block diagram which shows the whole steering apparatus for vehicles. It is a control block diagram for reaction force control by reaction force system ECU16. It is a graph which illustrates the relationship between steering angle (theta) h memorize | stored in reaction force torque-steering angle characteristic memory | storage part B4, and target reaction force torque. It is a steering control block diagram controlled by steering system ECU22. It is a graph which illustrates the relationship (stroke ratio) between steering angle (theta) h memorize | stored in the turning angle-steering angle characteristic memory | storage part C4, and a target turning angle.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic side view showing a schematic configuration of a forklift 1 as a cargo handling vehicle of the present invention. The forklift 1 steers a vehicle body 2, a cargo handling device 3 provided at the front of the vehicle body 2, a front wheel 5 as a drive wheel that supports the vehicle body 2, a rear wheel 6 as a steered wheel, and a rear wheel 6. A vehicle steering device 7 is provided.

  The vehicle steering device 7 is a so-called steer-by-wire power steering device in which the mechanical connection between the steering member 10 provided in the cab 8 and the rear wheel 6 that is a steered wheel is cut off. In this embodiment, the steering member 10 is a hand-wheeled steering wheel with a knob 10a, and the driver holds the knob 10a that is rotatably provided on the steering wheel, and rotates or stops the steering wheel.

  FIG. 2 is a configuration diagram illustrating the entire vehicle steering device 7. The vehicle steering device 7 includes a shaft 11 to which a steering member 10 is connected, a cylindrical column 12 that rotatably supports the shaft 11, a steering angle sensor 13 that detects a steering angle θh of the steering member 10, and a column. 12, a steering torque sensor 14 that detects the steering torque of the steering member 10, a reaction force motor 15 that functions as a reaction force actuator that applies a steering reaction force to the steering member 10 via the gear 17, and a reaction force A reaction force system ECU 16 (electronic control unit) 16 that drives and controls the motor 15 is provided. The steering torque sensor 14 detects the steering torque by detecting the torsion angle of a torsion bar interposed in the middle of the shaft 11. The steering angle sensor 13 detects the rotation angle of the shaft 11 by detecting the magnetism of a magnet attached to the outer periphery of the shaft 11 of the steering member 10 with a Hall sensor. In this embodiment, the steering angle sensor 13 detects the rotation angle from the neutral position of the steering member 10 in both forward and reverse directions, and the rotation angle from the neutral position to the right as a positive value. It is assumed that the rotation angle from the neutral position to the left is output as a negative value. The reaction force motor 15 is a DC motor that is installed on a separate axis from the shaft 11 and that rotates the shaft 11 at a predetermined gear ratio determined by the gear 17. The reaction force motor 15 may be arranged coaxially with the column.

  Further, the vehicle steering device 7 is moved by the rack shaft 17 that is held on the vehicle body and extends in the left-right direction of the vehicle, the rack support 18 that supports the rack shaft 17 so as to be movable, and the rack shaft 17. A steered motor 19, a steered system ECU 22 that drives and controls the steered motor 19, and a steered angle sensor 20 that detects a steered position of the rear wheels 6 (referred to as “steered angle” in this specification) ing. The steered motor 19 is a rack coaxial DC motor built in the rack support 18. The rotational motion of the steering motor 19 is converted into the reciprocating motion of the rack shaft 17 via the steering gear built in the rack support 18, and the tie rods 21 </ b> L connected to the pair of ends of the rack shaft 17, respectively. This is transmitted to the rear wheel 6 via 21R, whereby the rear wheel 6 is steered. The turning angle sensor 20 detects the displacement position of the rack shaft 17 with a stroke sensor by utilizing the correspondence between the displacement position of the rack shaft 17 and the turning angle of the rear wheel 6. The turning angle is detected.

Moreover, in order to steer the rear wheel 6 in accordance with the operation of the steering member 10, the reaction force system ECU 16 and the steering system ECU 22 are connected by an in-vehicle LAN (for example, CAN).
Further, a wheel speed sensor 34 for detecting the rotational speed of the wheel is attached to the rotor of the front wheel 5 or the rear wheel 6. The wheel speed sensor 34 optically reads the rotational speed of the wheel rotor, and detects the vehicle speed v by multiplying the read rotational speed by the effective rotational radius of the tire.

The steered system ECU 22 rotates the steered motor 19 based on the steering angle detected by the steering angle sensor 13. The rotation of the steered motor 19 is converted into a reciprocating motion of the rack shaft 17 via the steered gear, and is transmitted to the rear wheels 6 via tie rods 21L and 21R respectively connected to a pair of ends of the rack shaft 17. Thus, the rear wheel 6 is steered.
FIG. 3 shows a reaction force control block diagram controlled by the reaction force system ECU 16. A steering angle signal representing the detected steering angle θh is input from the steering angle sensor 13 to the target reaction force current calculation unit B1 of the reaction system ECU 16 via the in-vehicle LAN.

The reaction force torque-steering angle characteristic storage unit B4 including a nonvolatile memory stores the relationship between the steering angle θh and the target reaction force torque as a function.
The graph of “proposed characteristics” in FIG. 4 illustrates the relationship between the steering angle θh stored in the reaction force torque-steering angle characteristic storage unit B4 and the target reaction force torque. In this graph, when the first switching angle θh1 is set and the steering angle is in the first rudder angle region I equal to or smaller than the first switching angle θh1, the target reaction force torque is maximized as the steering angle increases. When the steering angle enters the second steering angle region II where the steering angle exceeds the first switching angle θh1, the target reaction force torque decreases monotonously from the maximum value as the steering angle increases. Yes. The target reaction force torque takes the lowest value within the range of the second steering angle region II at the upper limit steering angle θh3. The “upper limit steering angle θh3” is an angle at which the steering member 10 cannot be turned any more.

  The first switching angle θh1 is set to, for example, a steering angle of 90 degrees, and the upper limit steering angle θh3 is set to, for example, 810 degrees. The target reaction force torque takes a maximum value of 0.6 Nm when the steering angle is 90 degrees, which is the first switching angle θh1, and takes a minimum value of 0.15 Nm when the upper limit steering angle is 810 degrees. ing. Using a relationship between a steering angle and a turning angle of the rear wheel 6 described later (see the graph of “Proposed characteristics” in FIG. 6), a steering angle of 90 degrees is converted to a turning angle to be 8 degrees. When the upper limit steering angle 810 degrees is converted into a turning angle, it becomes 75 degrees.

In this embodiment, the first switching angle θh1 is set to 8 degrees in terms of the turning angle of the tire, but is not limited to 8 degrees. The first switching angle θh1 may be selected using as a guide the steering angle that is turned at the beginning of the turn. For example, the first switching angle θh1 may be selected from a range of 5 to 15 degrees in terms of the turning angle of the tire. Among these ranges, it is particularly preferable to select from a range of 8 to 10 degrees.
The target reaction force current calculation unit B1 converts the steering angle θh into a target reaction force current based on the relationship between the steering angle θh and the target reaction force torque described above. The target reaction force current is input to the current control unit B2. On the other hand, the current Im flowing through the reaction force motor 15 is detected, and an inverted signal thereof is input to the current control unit B2, and the current control unit B2 takes the difference between the target reaction force current and the current Im flowing through the reaction force motor 15. This difference is supplied to the PWM output circuit B3, and a PWM drive signal for driving the reaction force motor 15 is generated. By supplying this PWM drive signal to the reaction force motor 15, reaction force torque is applied to the steering member 10 via the reaction force motor 15 → the gear 17 → the shaft 11.

Next, FIG. 5 shows a steering control block diagram controlled by the steering system ECU 22. A steering angle signal representing the detected steering angle θh is input from the steering angle sensor 13 to the target turning angle calculation unit C1 of the steering system ECU 22 via the in-vehicle LAN.
The turning angle-steering angle characteristic storage unit C4 including a non-volatile memory stores the relationship between the steering angle θh and the target turning angle as a function.

  FIG. 6 illustrates a relationship (stroke ratio) between the steering angle θh stored in the turning angle-steering angle characteristic storage unit C4 and the target turning angle. In this graph, a second switching angle θh2 larger than the first switching angle θh1 and smaller than the upper limit steering angle θh3 is set, and the ratio of the steering angle to the steering angle is such that the steering angle is the first switching angle θh1. In the steering angle region II-1 from the second switching angle θh2 to the second switching angle θh2, the first inclination is taken, and in the steering angle region II-2 from the second switching angle θh2 to the upper limit steering angle θh3, the steering angle A second inclination smaller than the first inclination is taken. That is, if the inclination (conventional characteristic) obtained by connecting the turning angles with a straight line from the first switching angle θh1 to the upper limit steering angle θh3 is “third inclination”, the first inclination> third inclination> second The inequality of the slope is established.

The second switching angle θh2 is set to a steering angle of 400 degrees, for example. When the steering angle of 400 degrees is converted into the target turning angle, it becomes 51 degrees. In this embodiment, the second switching angle θh2 is set to 51 degrees in terms of the turning angle of the tire, but is not limited to 51 degrees. The second switching angle θh2 may be selected from the first switching angle θh1 and the upper limit steering angle.
With this setting, when the cargo is unloaded (loading work) after the forklift has cornered at right angles, the steering angle when stopped in front of the load is in the region II-2. When performing fine adjustment steering (cutting and returning) of the tip in the left-right direction in the II-2 region, the steering ratio is slow, so that the work becomes easy.

Depending on the vehicle speed v, it is possible to set the overall stroke ratio to be smaller as the speed v is higher, and to increase the overall stroke ratio as the speed v is slower.
The target turning angle calculation unit C1 converts the steering angle θh into the target turning angle based on the relationship between the steering angle θh and the target turning angle described above. The signal of the target turning angle is input to the current control unit C2. On the other hand, the turning angle of the rear wheel 6 is detected by the turning angle sensor 20, and an inverted signal thereof is input to the current control unit C2. The current control unit C2 detects the target turning angle and the detected value of the turning angle of the rear wheel 6. And the difference is supplied to the PWM output circuit C3, and a PWM drive signal for driving the steered motor 19 is generated. Then, by supplying this PWM drive signal to the steering motor 19, the rotation is converted into a parallel motion of the rack shaft 17, and transmitted to the rear wheel 6 via the tie rods 21L, 21R, whereby the rear wheel 6 rotates. Steered.

  As described above, according to the embodiment of the present invention, the driver of the forklift 1 starts turning the steering member 10 at the beginning of turning at the time of turning of the vehicle, that is, in the first rudder angle region I, and performs the first switching. Since the forklift 1 is steered while feeling a large steering reaction force up to the angle θh1, there is little possibility that the steering member 10 is turned too much beyond the driver's intention to turn the front lightly at a small steering angle. In the latter half of the turn, the steering angle is in the second steering angle region II that exceeds the first switching angle θh1. At this time, since the steering reaction force monotonously decreases from the maximum value as the steering angle increases, the driver feels that the reaction force decreases as the steering member 10 is turned. Accordingly, the driver can easily swing the rear portion of the forklift 1 by turning the steering member 10 with less force.

  Further, in the first half steering angle region II-1 of the second steering angle region II, the forklift 1 can be steered at a rapid ratio, and in the second half steering angle region II-2, the forklift 1 is steered at a moderate ratio. be able to. Therefore, compared to the conventional constant ratio in which the turning angles are connected by a straight line from the first switching angle θh1 to the upper limit steering angle θh3, the first half rudder has a relatively large steering reaction force even though it is reduced from the maximum value. When in the corner region II-1, the steering member 10 can be swiveled greatly by turning a little. When the steering reaction force is in the second half steering angle region II-2 where the steering reaction force is further lowered, the steering member 10 must be rotated more. However, since the steering reaction force is reduced, the burden on the driver is small. In addition, when the cargo handling operation is performed in the region II-2, since the steering ratio is slow, the fork tip positioning operation is facilitated.

By adopting both the setting of the steering reaction force according to the steering angle and the setting of the steering ratio according to the steering angle in this manner, the driver can easily steer suddenly with a small force, and the driver's steering burden Can be reduced.
Although the embodiment of the present invention has been described above, the implementation of the present invention is not limited to the above-described embodiment. For example, instead of the configuration in which the rear wheels 6 are provided on the left and right sides of the vehicle body 2 as steered wheels, a single rear wheel 6 may be provided at the center in the left-right direction of the vehicle body 2. In the above-described embodiment, the rack shaft 17 driven by the steered motor 19 is adopted as the steered wheel drive mechanism. However, a hydraulic cylinder driven by an electric hydraulic pump may be adopted. In addition, various modifications can be made within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Forklift (cargo handling vehicle), 2 ... Vehicle body, 3 ... Cargo handling device, 5 ... Front wheel (drive wheel), 6 ... Rear wheel (steered wheel), 7 ... Steering device for vehicles, 10 ... Steering member, 13 ... Steering angle Sensor: 14 ... Steering torque sensor, 15 ... Reaction force motor, 16 ... Steering side ECU, 17 ... Rack shaft, 19 ... Steering motor, 20 ... Steering angle sensor, 22 ... Steering side ECU

Claims (4)

A steering apparatus for a cargo handling vehicle that employs a steer-by-wire system in which mechanical connection between a steering member and a steered wheel drive mechanism is broken,
Driving said steered wheel drive mechanism for steering the steered wheels, the steering angle detection unit that detects a steering angle of the steering member, a reaction force actuator that imparts a steering reaction force to the steering member, the steering wheel drive mechanism A steering actuator that controls the steering actuator, a second steering actuator that controls the steering actuator, and a second steering angle that is in a first steering angle region that is equal to or less than the first switching angle or that exceeds the first switching angle. A steering area determination unit that determines whether the steering angle is in the steering angle area; and when the steering angle is in the first steering angle area, the steering reaction force is raised to the maximum value as the steering angle increases, and the steering angle is the second the steering reaction force with increasing steering angle and entering the steering angle region and a reaction force actuator control unit that controls the reaction force actuator so as to decrease from the maximum value, the steering apparatus for a cargo handling vehicle. A second switching angle larger than the first switching angle is set;
The steered actuator controller has a ratio of the steered angle to the steered angle, wherein the steered angle takes a first inclination from the first switching angle to the second switching angle, and the steering angle is the second The steering device for a cargo handling vehicle according to claim 1, wherein the steering actuator is controlled to take a second inclination smaller than the first inclination at a switching angle greater than or equal to. The cargo handling vehicle steering device according to claim 1 or 2, wherein the first switching angle is 5 to 15 degrees in terms of a turning angle of a steered wheel. The steering apparatus for a cargo handling vehicle according to claim 3, wherein the first switching angle is 8 to 10 degrees in terms of a turning angle of a steered wheel.

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